Hyperbranched polymers classified as dendritic polymers have a specific structure having intentionally introduced branches. With such a structure, dendritic polymers have various characteristics in a respect of having a nanometer size, a respect of being capable of forming surfaces having many functional groups, a respect of being rendered having a low viscosity compared to linear polymers, a respect of exhibiting a behavior like fine particles with little entanglement between molecules, a respect of being capable of becoming amorphous with their solubility in a solvent controllable, and the like. Accordingly, various practical applications are expected utilizing these characteristics.
Particularly, having a large number of terminal groups is regarded as the most remarkable characteristic of dendritic polymers. In such a dendritic polymer having a large number of terminal groups, intermolecular interactions depend largely on the types of the terminal groups, resulting in large variations in its glass transition temperature, solubility, thin film forming properties, or the like. Accordingly, such a dendritic polymer has characteristics which no general linear polymer has. When reactive functional groups are added as terminal groups to such a dendritic polymer, the polymer has reactive functional groups in extremely high density. Therefore, its applications as, for example, a high sensitive scavenger for functional substances such as a catalyst, a high sensitive multifunctional crosslinking agent, a dispersant or a coating agent for metals or metal oxides are also expected. That is, in dendritic polymers, selection of the types of the terminal groups becomes an important factor for exhibiting characteristics of the polymer.
An advantage of the hyperbranched polymer over other dendrimers is in its simplicity for synthesis, which is extremely advantageous particularly in an industrial production. Generally, while the dendrimer is synthesized by repeating protection and deprotection, the hyperbranched polymer is synthesized by a one-step polymerization of a so-called ABx type monomer having in one molecule thereof, a total of three or more substituents of two types.
As a synthesis method thereof, known is a method for synthesizing a hyperbranched polymer by a living radical polymerization of a compound having a vinyl group while having a photo-polymerization initiating ability. For example, known are a synthesis method of a hyperbranched polymer by a photo-polymerization of a styrene compound having a dithiocarbamate group (see Non-Patent Documents 1, 2 and 3), and a synthesis method of a hyperbranched polymer having a dithiocarbamate group by a photo-polymerization of an acrylic compound having a dithiocarbamate group (see Non-Patent Documents 4, 5 and 6).